1. Technical Field
The present invention relates to rotating electric machines that are used in, for example, motor vehicles as electric motors and electric generators.
2. Description of Related Art
FIG. 13 shows the overall configuration of a conventional rotating electric machine for a vehicle. As shown in the figure, the conventional rotating electric machine includes a rotating shaft 120, a rotor 130, a stator 140 and a cooling device 170. The rotating shaft 120 is rotatably supported by a housing of the machine via bearings. The rotor 130 is fixed on the rotating shaft 120 so as to rotate with the rotating shaft 120. The stator 140 includes an annular stator core 150 that is disposed radially outside the rotor 130 so as to surround the rotor 130, and a stator coil 160 that is mounted on the stator core 150 so as to have a pair of coil ends 161 and 162 protruding axially outward respectively from opposite axial end faces of the stator core 150. The cooling device 170 is provided to supply cooling liquid to vertically upper parts of the coil ends 161 and 162 of the stator coil 160.
During operation of the machine, electric current flows in the stator coil 160, thereby generating heat. Therefore, it is necessary to cool the stator coil 160.
To this end, the cooling device 170 is configured, for example as disclosed in Japanese Unexamined Patent Application Publication No. 2006-115651, to have a pair of cooling pipes 171 and 172 respectively located vertically upward of the coil ends 161 and 162 of the stator coil 160. Consequently, it is possible to supply the cooling liquid to the vertically upper parts of the coil ends 161 and 162 via the cooling pipes 171 and 172.
However, with the above configuration, it may be difficult to sufficiently cool vertically lower parts of the coil ends 161 and 162 of the stator coil 160.
More specifically, with the above configuration, the cooling liquid may flow from the upper parts to the lower parts of the coil ends 161 and 162 by gravity along the surfaces of the coil ends 161 and 162, i.e., flow along first flow paths 101 as shown in FIG. 14. In this case, the temperature of the cooling liquid will be increased by heat conducted from the coil ends 161 and 162 to the cooling liquid during the flow of the cooling liquid along the first flow paths 101. Consequently, with the cooling liquid whose temperature has been increased, it may be difficult to sufficiently cool the lower parts of the coil ends 161 and 162.
On the other hand, depending on the positions of the cooling pipes 171 and 172, the flow rate of the cooling liquid and the shapes of the coil ends 161 and 162, the cooling liquid may directly fall down through gaps or void spaces formed in the coil ends 161 and 162, i.e., flow directly downward along second flow paths 102 as shown in FIG. 14. In this case, it may be difficult to supply a sufficient amount of the cooling liquid to the lower parts of the coil ends 161 and 162. Consequently, it also may be difficult to sufficiently cool the lower parts of the coil ends 161 and 162.